This manual presents detailed guidelines and procedures for developing transmission line structure loads. It is divided into four sections. The first section is concerned with the load/strength design format. It introduces a reliability-based design methodology that forms the framework for the loading guidelines. A load and resistance factor design (LRFD) format is presented for the design of any transmission structure. The nature and variability of loads are given along with detailed procedures for the selection of the load and resistance factors. The next section discusses weather related loads. It gives specific procedures and formulas for determining weather related loadings on transmission line structures that can be used in the reliability-based design methodology described in section one. The third part presents a detailed discussion on special loadings such as longitudinal loads, construction and maintenance loads, line galloping, and structure vibration. The final section provides a detailed numerical example of the loading computations based on the procedures given in this guide.